Matsumoto does do a couple of special programs like Suberanai Hanashi and Ippon Grand Prix, which is a comedian contest to see who can come up with the best jokes to certain questions.
2ch is known to be quite harsh to other comedians as well, aren't they? It's why I mostly give little heed to their opinions since you get a hell of a lot of negativity and rarely any positives on any comedians. I still remember someone saying on 2ch that if everyone who used it were subjected to a Negativity Prohibited-style activity, all of them would be punished because they'd been too negative in their posts

. In terms of the discussions about the duo, there are several main things that I have seen been commonly raised in Downtown 2ch threads:
- Matsumoto has gotten less funny since his marriage in 2009. I can't tell you how many times I have seen them raise the finger at this as a reason he's not funny anymore. They also joke that he's been working out so much in the gym that he's left his comedic sense in there and maybe he should get a divorce so he can be funny again, which I really don't understand
- 2ch users like Hamada more nowadays as they feel unlike Matsumoto, he hasn't changed much and still can be depended on to provide a good foil for the people he works with.
- Most want the free talk manzai-style corner back in Gaki or just want to see them perform simple manzai again. However much Downtown may be polarising to 2ch users, most of them agree that their strength is their manzai routine and that they're still amongst the top tier of comedians when it comes to improvisation.
- Hamada is seen by 2ch to be able to work efficiently on his own hosting the various shows that you mentioned above (Gobu Gobu) etc. For some reason, they think Matsumoto on his own wouldn't be able to work properly on solo shows (ironically, his Suberanai Hanashi series and Ippon Grand Prixs have gotten solid ratings)
I won't go any further because the constructive criticism ends there and it just descends into chaos there (repeated gloating and trolling from hardcore fans of rival comedians (particularly Tunnels and Ucchan Nanchan fans) about Downtown's bad TV ratings, jibes about his looks, racist stuff about his wife who is apparently half-Korean etc.), but Matsumoto certainly cops the brunt of criticism when it comes to discussions like these. Why, I don't know, given I don't think he's changed a lot but then 2ch isn't known for rational, well-thought out discussion, are they?